Acids, Bases and pH scale

ACIDS

• Compound that releases Hydrogen ions (H+)

Examples of Common Acids

• Hydrochloric acid – HCl• Hydrosulfuric acid – H2SO4

• Nitric acid – H2NO3

What do these formulas have in common?

Acetic Acid - Vinegar

HC2H3O2

Lactic Acid

•Found in foods like yogurt and cottage cheese and sourdough bread

•Causes muscle soreness

Citric Acid

•Found abundantly in citrus fruits (lemons, oranges, grapefruit)•Used to add a sour taste to foods •Flavoring in soft drinks

Formic Acid

• In the venom of ants and bees HCO2H

Amino Acids• “Building blocks” of protein molecules

Bases

•Bases are compounds that release Hydroxide ions (OH -) in water. • Also called alkalines.

Examples of Common Bases

Sodium hydroxide – NaOHCalcium hydroxide – CaOHMagnesium hydroxide – Mg(OH)2

Most soaps and detergents are basic

All compounds are eitherAcids, Bases, or Neither

HFH2SO4

CaOHMg(OH)2

C6H12O6

HClNaClAl(OH)2

Chemical Formula Acid Base Neither

pH

The measurement of the amount of H+ (hydrogen ions) in solution

pH Scale - Range is 0 - 14

0 1 2 3 4 5 6 7__ 8 9 10 11 12 13 14

http://upload.wikimedia.org/wikipedia/commons/4/46/PH_scale.png

1.311.477.0010.16.9993.8913.00.0

pH Acid Base Neutral

Determining a compound’s property from its pH value

Most living things must live in an environment of pH 6.5 – 7.5

HOWEVER, there are some exceptions:

•Acidophiles – bacteria that live in highly acidic environments. They have evolved a variety of specialized mechanisms to maintain their intracellular pH at a constant level (usually 7.2). Example: L. acidophilus breaks down food in the intestine

• Specialized cells in stomach lining make HCl “stomach acid” of pH 1

Parietal Cells

• Azalea plants thrive in acidic soil of pH 4.5

Soil pH

• Alkaline soil makes hydrangeas pink

• Acidic soil makes hydrangeas blue

Buffers

• Help prevent any large changes in pH

• Buffers are molecules that can bind to an H+ ion when the H+ concentration increases - “locks” it up so the solution doesn’t get more acidic

• Releases an H+ ion when the H+ concentration decreases

Blood pH and Buffers

• Normal pH of blood between 7.35 - 7.45

• Less than 6.8 or greater than 7.8 is deadly

• Buffers in blood help prevent any large change in blood pH

Lysergic acid diethylamide